Twixtor: 30p to 24p in After Effects

RE:Vision Effects does one thing, image manipulation. And they do it very well
By Jeremiah Hall

When talkies came on the scene, studios had to make a choice. What frame rate would be the new standard? The old silent film rate of 18FPS wasn't fast enough to support sound with the technology of the day. So they experimented. The slowest they could run film that would support sound was 24fps (frames per second). The slower the speed, the less film they had to buy, process, and ship out for projection to theaters across the country. So for theatrical film, 24FPS became King of the World.

Enter television. 1940s television worked on an interlaced-frame model of 30fps, based on the U.S. electric frequency of 60Hz. In most of Europe electrical frequency is 50Hz, leaving broadcasters with a 25FPS frame rate. Two mediums, three frame rates.

Fast forward to the 21st Century. HDTV is the new King. Consumer and prosumer cameras record progressive, with a variety of frame rates, including 24FPS, 25FPS, 30I, 30P. Some filmmakers are shooting 60P video for theatrical distributions. What does this mean? If you're doing visual effects, it means you're going to eventually have a headache. I'm working on a project now that was shot 24p. The director wants an effect added in, a blood spurt that was shot in 30P.

After Effects alone will let me convert footage to 24P. However, I was not entirely happy with the motion of the clip once I was finished. It looked blocky, and clearly had lost some of the fluid splash from the original that I needed for the final shot. Enter Twixtor (Figure 1).

Figure 1 Click Image To Open Larger View (You may need to make sure pop up blockers are not enabled.)

Twixtor, from Re:Vision Effects, Inc., has been around for a while. Currently it is in version 5.0. It works with Adobe After Effects, Adobe Premiere Pro, Apple Final Cut Pro (X and 7), Autodesk combustion, flame, Maya Composite, Avid, Foundry Nuke, Sony Vegas Pro, and several others. It changes speed, timing, and frame rates of footage (frame rate conversion is currently only available with After Effects or combustion). Twixtor does this by warping and interpolating new frames from the original footage using RE:Vision's proprietary tracking technology to calculate every individual pixel's motion in a sequence.

The footage I needed to use came from Detonation Films, www.detfilmshd.com, from one of their Hemostock packages. This was for a project I'm doing visual FX on, a short film titled "Hellevator," (www.hellevatormovie.com) directed by Heath McKnight and written by comic book legend David Michelinie (Iron Man, Superman). The footage was shot in 30P. My final sequence and original green-screen layer was 24P.

Basic Twixtor has a few settings to adjust ranging from input settings, including the source's field order and frame rate; track control, for motion vector calculations and pixel motion sensitivity; to output, which gives you time remapping options, frame interpretation options, and motion blur.

Output settings in After Effects are a snap - it is done for you. Twixtor uses After Effects own composition settings for the output settings.

One of the more interesting settings I found was Image prep. You have two choices, None and Contrast/Edge Enhance. Contrast/Edge Enhance is for footage where there are many poorly-defined edges in the shot or the shot has very little contrast for Twixtor to work with.

I put the footage on the timeline, added Twixtor, set my parameters, and previewed. Then I hit Make Movie. My 30P blood spray was now a 24P blood spray. I could now take the footage and add it to the victi-, uh, actor in my violent shot.

But how does it compare to After Effects own conversion? Here are frames 9-12 from After Effects (See Fig. 2). Here are the frames from Twixtor (see Fig. 3). Twixtor's interpretation of the footage was closer to the original footage to me, and more importantly to the client.

Figure 2

Figure 3

Is it worth the money? Twixtor is $329.95 from Re:Vision Effects' website, available for all major NLEs including Final Cut Pro X, Final Cut 6, Final Cut 7, Avid, Vegas Pro, Premiere Pro, etc., while Twixtor Pro comes in at $595.00, pricing as of May, 2012 - After Effects and Premiere Pro only. If you routinely have to retime footage, and who doesn't, the answer is yes.

Re:Vision Effects does offer frame rate conversion for Vegas, FCP and Avid, here are the links to the tutorials.

I few years ago I needed to replace a surround sound receiver. As I was standing at the store, I started looking at two models. The features of the two were similar, as was the price. Model A was made by a large firm that made electronic everything. Model B was made by a company who made audio equipment their area of expertise, and that was it - no televisions, game platforms, GPS navigation, nada. I listened to both of them. Same piece of music, same EQ settings. I came home with Model B. Both Models did the exact same thing, but Model B sounded better.

Our business is aesthetics; After Effects alone and After Effects with Twixtor both do the same thing: convert 30P to 24P. But the final conversion and output of the Twixtor plugin looked better to both me and the client, making the client happy.

RE:Vision Effects does one thing, image manipulation. And they do it very well. Check out Twixtor at www.revisionfx.com.